1. Field of the Invention
The present invention generally relates to an antiglare film, a manufacturing method thereof, and a transmissive liquid crystal display. More particularly, the present invention relates to: an antiglare film that is provided on a surface of a window, or on a surface of a display such as a liquid crystal display (LCD), a CRT display, an electroluminescent display (ELD), a plasma display (PDP), a surface-conduction electron-emitter display (SED) or a field emission display (FED); a manufacturing method thereof, and a transmissive liquid crystal display.
2. Description of the Background Art
In the field of displays such as liquid crystal displays, CRT displays, EL displays, and plasma displays, an antiglare film having a concave-convex structure on its surface is provided on the display surface in order to prevent a reduction of visibility caused by reflection of external light on the display surface during viewing.
The following are some techniques for manufacturing an antiglare film having a concave-convex structure on its surface: a technique of forming a concave-convex structure on a surface of an antiglare film by embossing; and a technique of applying a coating liquid, which is obtained by mixing particles into a binder matrix forming material and dispersing the particles in the binder matrix, on a transparent substrate to form a concave-convex structure on an antiglare film. Since the antiglare film thus formed is provided with the concave-convex structure on its surface, external light incident on the antiglare film is scattered by the concave-convex structure on the surface, and thereby an image of the external light becomes smudgy. That is, a reduction of visibility caused by reflection of the external light on the display surface can be prevented.
In the antiglare film having, on its surface, concavities and convexities formed by embossing, the convexities and concavities on the surface can be controlled by managing a pattern of an embossing roll. Therefore, reproducibility is good. However, if the embossing roll has a defect or a foreign matter attached thereto, a defect will periodically appear on the antiglare film that extends from the roll.
Various forms of antiglare films, each having an antiglare layer in which particles are dispersed in a binder matrix, have been disclosed in patent documents. An antiglare film using a binder matrix and particles for forming an antiglare layer, which is disclosed in Patent Document 1, requires less process steps for production and therefore can be produced at a lower cost as compared with the above-described antiglare film produced using the emboss processing (refer to Patent Document 1).
Patent Document 2 discloses a technique using a combination of a binder matrix resin, spherical particles, and irregular-shape particles for forming an antiglare layer (refer to Patent Document 2). Patent Document 3 discloses a technique using a binder matrix resin and a plurality of kinds of particles having different diameters for forming an antiglare layer (refer to Patent Document 3). Patent Document 4 discloses a technique in which, in an antiglare film having concavities and convexities on its surface, the cross-sectional area of the concavities is specified (refer to Patent Document 4).
Furthermore, Patent Document 5 discloses a technique of providing an antiglare property by using a combination of internal scattering and surface scattering of an antiglare layer, that is, a technique in which the internal haze value (cloudiness) of the antiglare layer is set to be in the range of 1% to 15% and the surface haze value (cloudiness) thereof is set to be in the range of 7% to 30% (refer to Patent Document 5). Patent Document 6 discloses a technique for forming an antiglare layer, in which a binder resin and particles having diameters in the range of 0.5 μm to 5 μm are used, a difference in the refractive index between the binder resin and the particles is set to be in the range of 0.02 to 0.2, and the particles are blended in an amount greater than 10 parts by weight and less than 30 parts by weight into 100 parts by weight of the binder resin (refer to Patent Document 6), Patent Document 7 discloses a technique for forming an antiglare layer, in which a binder resin and particles having diameters in the range of 1 μm to 5 μm are used, a difference in the refractive index between the binder resin and the particles is set to be in the range of 0.05 to 0.15, and a solvent to be used, surface roughness, and the like are set within predetermined ranges (refer to Patent Document 7). Patent Document 8 discloses a technique in which a binder resin and a plurality of kinds of particles are used, and a difference in the refractive index between the binder resin and the particles is set to be in the range of 0.03 to 0.2 (refer to Patent Document 8). Patent Document 9 discloses a technique in which, in order to prevent a reduction in contrast, hue variation, and the like when a viewing angle is changed, the surface haze value (cloudiness) at the surface of an antiglare film is set to be 3 or more, and a difference between the haze value in the normal direction and the haze value in the direction at ±60° is set to 4 or less (refer to Patent Document 9).
As described above, antiglare films of various configurations have been discovered to attain a variety of results. The performance of an antiglare film used on the front surface of a display varies depending on the type of the display. In other words, selection of an appropriate antiglare film depends on the resolution of the display or intended use of the display. Therefore, a variety of antiglare films are required according to the intended purposes.
The antiglare films disclosed in Patent Documents 1 to 9 are provided on the surfaces of liquid crystal displays for notebook PCs, desktop PCs, or televisions. However, in manufacturing of antiglare films intended to be used on only the display surfaces of televisions, a lot of unnecessary parts that are useless because of the sizes are caused by chamfering, which results in an increase in cost.
Therefore, in recent years, there has been increased demand for an antiglare film that can be used on the display surface of any of notebook PCs, desktop PCs, and televisions.
In the related art, however, sufficient contrast cannot be obtained if an antiglare film intended for notebook PCs or desktop PCs is used on a display of a television. Conversely, if an antiglare intended for television displays is used for a notebook PC or a desktop PC, a phenomenon of image flickering (glare) cannot be sufficiently prevented.
Furthermore, an antiglare film intended for notebook PCs or desktop PCs may require a high level of glare suppression, because a user (observer) continuously observes and stares at a display surface for long hours. On the other hand, an antiglare film intended for televisions may require image display at a high contrast when provided on a display surface in order to prevent sharpness of the image from deteriorating.
Patent Document 1: Japanese Laid-Open Patent Publication No. 6-18706
Patent Document 2: Japanese Laid-Open Patent Publication No. 2003-260748
Patent Document 3: Japanese Laid-Open Patent Publication No. 2004-004777
Patent Document 4: Japanese Laid-Open Patent Publication No. 2003-004903
Patent Document 5: Japanese Laid-Open Patent Publication No. 11-305010
Patent Document 6: Japanese Laid-Open Patent Publication No. 2002-207109
Patent Document 7: Japanese Laid-Open Patent Publication No. 2000-338310
Patent Document 8: Japanese Laid-Open Patent Publication No. 2000-180611
Patent Document 9: Japanese Laid-Open Patent Publication No. 11-160505